1. Field of the Invention
The present invention relates generally to high-temperature stable polyimides. It relates particularly to aromatic polyimides which contain dimethylsilane in the dianhydride and --CF.sub.3 groups in the diamine portion of the polymer chain.
2. Description of the Related Art
Because of their outstanding thermal stability, low density, resistance to radiation, toughness and flexibility, linear aromatic polyimides are being used increasingly for applications in space. Polyimides are also being exploited by the electronics industry as film and coating materials in the production of advanced microelectronic circuitry.
To be useful as a film or coating material for microelectronics applications, a polymer must be an excellent insulator and have a low dielectric constant. The lower the dielectric constant of the candidate polymer, the more efficient the circuit. The dielectric constant of commercially available, state-of-the-art polyimide film presently used for electronics applications ranges from about 3.2 to 4.0 at 10 GHz depending upon moisture content. It is an object of the present invention to provide polyimides which possess dielectric constants in the range of about 2.5 to 2.8 at 10 GHz, which afford a much improved circuit system.
The need exists also for high-temperature, highly optically transparent or colorless film and coating materials for applications on large space components such as solar cells, space mirrors, thermal control coating systems, antennae and many others. Commercial polyimide film is known for its bright yellow color, and it is not efficient in its transmission of solar energy. Accordingly, another object of the present invention is to provide polyimides which are highly optically transparent and therefore are significantly more efficient than currently used materials for these applications.